This invention relates generally to inflatable restraint systems and, more particularly, to actuation systems such as for use in the inflation of inflatable devices such as inflatable vehicle occupant restraint airbag cushions used in inflatable restraint systems.
Inflatable safety restraint installations typically employ an inflator device to produce inflation gas for inflating a vehicle occupant restraint airbag cushion in the event of a collision. Such inflator devices often include a gas generant material stored within an inflator device housing and an initiator in combination with the housing that actuates the gas generant material. The initiator typically includes a reactive charge in combination with electrical connectors. A signal sent through the electrical connector(s) actuates the reactive charge, which produces reaction products that actuate the gas generant material.
In view of possibly varying operating conditions and, in turn, possibly varying desired performance characteristics, inflatable safety restraint technology has lead to the development of what has been termed “adaptive” or “Smart” inflator devices and corresponding inflatable restraint systems. With an adaptive inflator device, output parameters such as one or more of the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.
Pyrotechnic inflators typically may have one or more chambers containing gas generant. Adaptive pyrotechnic inflators having gas generant material in two chambers, which are independently ignited via respective initiators or igniters have been referred to as “dual stage” inflators. In practice, each such gas generant material-containing chamber is oftentimes referred to as a “combustion chamber” as the gas generant material therein contained is burned or otherwise reacted to produce or form gas such as may be used to inflate an associated inflatable restraint airbag cushion.
Dual stage inflators may have several contemplated actuation or firing scenarios. In a first such scenario, only the gas generant material in a first or primary chamber and associate initiator device is actuated whereby a fixed quantity of inflation gas is produced thereby. In a second possible scenario, the first or primary initiator is first actuated whereby gas generant material in a first chamber is first reacted to start to produce or form inflation gas and after a predetermined or preselected delay, a secondary initiator is then actuated whereby gas generant material in the second chamber is reacted to also produce or form inflation gas. In a third possible scenario, both the primary and the secondary initiators are actuated whereby a gas generant material in a first chamber and a gas generant material in a second chamber are actuated simultaneously to produce or form inflation gas from the gas generant material in each of the chambers.
As will be appreciated, through the selection and use of an appropriate such actuation or firing scenario, inflator output parameters such as one or more of the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as one or more of ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.
Current “Smart” systems, employing two stages, or Dual Stage systems for airbag inflators commonly utilize two separate initiator assemblies. In the current state of automotive airbag technology, dedicated wiring is commonly employed to direct safety device function signals from a Restraint Control Module (RCM) to each device being commanded to deploy. Further, each individual initiator assembly is typically either injection molded or crimped into a respective supporting adapter. Each initiator assembly typically will include or have dedicated pins and associated connectors that direct the operating current to the respective initiator. Thus, the evolution of the technology to “Smart” systems, employing two stages, or Dual Stage systems for airbag inflators, has lead to an increase in the number of individual actuation or firing loops, connectors, output pins and RCM connectors required for providing or resulting in the desired range of operation for a particular inflatable restraint system. As a result, such Dual Stage systems are typically larger in packaging size, heavier in weight and more complex in operation, than may otherwise be desired.
Thus, there is a need and demand for Dual Stage systems and component(s) thereof and associated methods of operation of increased simplicity and reliability of operation and design. In particular, there is a need and demand for Dual Stage systems and component(s) thereof and associated methods of operation that provide or result in specifically desired inflation performance scenarios in a less costly and/or more efficient manner (e.g., one or more of reduced size, weight and/or complexity of operation).